linux-kernel - Re: [PATCH 7/9] mm, slub: introduce kmem_cache_debug

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Date:   Thu, 18 Jun 2020 10:32:18 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        vinmenon@...eaurora.org, Matthew Garrett <mjg59@...gle.com>,
        Roman Gushchin <guro@...com>, Jann Horn <jannh@...gle.com>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: Re: [PATCH 7/9] mm, slub: introduce kmem_cache_debug_flags()

On 6/17/20 7:56 PM, Kees Cook wrote:
> On Wed, Jun 10, 2020 at 06:31:33PM +0200, Vlastimil Babka wrote:
>> There are few places that call kmem_cache_debug(s) (which tests if any of debug
>> flags are enabled for a cache) immediatelly followed by a test for a specific
>> flag. The compiler can probably eliminate the extra check, but we can make the
>> code nicer by introducing kmem_cache_debug_flags() that works like
>> kmem_cache_debug() (including the static key check) but tests for specifig
>> flag(s). The next patches will add more users.
>> 
>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>> ---
>>  mm/slub.c | 18 ++++++++++++++----
>>  1 file changed, 14 insertions(+), 4 deletions(-)
>> 
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 24d3e5f832aa..c8e8b4ae2451 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -122,18 +122,28 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
>>  #endif
>>  #endif
>>  
>> -static inline int kmem_cache_debug(struct kmem_cache *s)
>> +/*
>> + * Returns true if any of the specified slub_debug flags is enabled for the
>> + * cache. Use only for flags parsed by setup_slub_debug() as it also enables
>> + * the static key.
>> + */
>> +static inline int kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
> 
> This should return slab_flag_t, yes?

bool, actually

>>  {
>>  #ifdef CONFIG_SLUB_DEBUG
>>  	if (static_branch_unlikely(&slub_debug_enabled))
>> -		return s->flags & SLAB_DEBUG_FLAGS;
>> +		return s->flags & flags;
>>  #endif
>>  	return 0;
>>  }
>>  
>> +static inline int kmem_cache_debug(struct kmem_cache *s)
> 
> And this too, as long as we're making changes here.

OK